Shock absorber defective

What causes it

• Wear of the internal seal and valving, which sets in gradually from somewhere around 60,000 to 80,000 miles
• A stone chip or corrosion pitting the piston rod, which then cuts the seal on every stroke
• A collapsed top mount or crumbled bump stop putting the damper out of line
• Overloading, regular towing, or a heavy pothole strike bending the rod

Advisory or failure?

Slight misting on the body of a damper is a minor defect and does not fail the car. A shock absorber that is leaking severely, obviously not damping, insecure, damaged or missing is a major defect. Where the condition is bad enough to compromise the vehicle's stability — a damper detached from its mounting, for instance — the grading is dangerous. Most testers assess this visually for leaks and security alongside a bounce test at each corner; where a suspension damping performance test is used instead, a difference of more than 30% between the two sides of an axle is also a major defect.

Can you fix it yourself?

Possible with care

Rear dampers on many cars are two bolts and a genuinely simple job. Front struts are not. The coil spring on a strut stores enough energy to kill, and releasing it needs proper matched spring compressors in good condition — the cheap hook-type clamps sold in bargain sets are exactly the ones that slip. Buying complete pre-assembled struts avoids handling the spring at all and is worth the extra. Dampers are replaced in pairs across an axle whichever route you take, or the car brakes and corners unevenly, and struts carry the camber setting so the alignment must be checked afterwards.

What it costs

A pair of rear dampers is £60 to £140 in parts with about an hour and a half of labour, landing near the bottom of the band. A pair of front struts is more like £120 to £250 in parts and two to three hours, plus alignment, which reaches the top. Complete strut assemblies cost more in parts but save enough labour to be the better value on many cars. Electronically adaptive dampers, fitted to many premium and performance models, sit well beyond this band — a single unit can cost more than a conventional pair.

What happens if you ignore it

Worn dampers lengthen stopping distances, because the tyres spend part of every bump lightly loaded or off the road entirely, and they undermine the ABS and stability systems that assume the wheels stay planted. The car becomes unpredictable in an emergency swerve, which is precisely when you need it not to be. In the meantime the uncontrolled movement chews through tyres and loads up the springs, top mounts and bushes around it.

Common questions

Do leaking shock absorbers fail an MOT?

Slight misting on the body of a damper is a minor defect and does not fail the car. A shock absorber that is leaking severely, obviously not damping, insecure, damaged or missing is a major defect. Where the condition compromises the vehicle's stability, a damper detached from its mounting for instance, the grading is dangerous.

How can I tell if my shock absorbers are worn?

Push down hard on one corner and let go: a healthy damper settles in a single movement, while a worn one lets the car bob for a second or two. Look for an oily film down the damper body with road dirt stuck to it, and check the tread for cupped or scalloped wear. Where a damping performance test is used, more than 30% difference across an axle is a major defect.

Can I replace shock absorbers myself?

Rear dampers on many cars are two bolts and a genuinely simple job. Front struts are not. The coil spring stores enough energy to kill, and releasing it needs proper matched spring compressors in good condition, not the cheap hook-type clamps sold in bargain sets. Buying complete pre-assembled struts avoids handling the spring at all and is worth the extra.

How much does it cost to replace shock absorbers?

A pair of rear dampers is £60 to £140 in parts with about an hour and a half of labour. A pair of front struts is £120 to £250 in parts and two to three hours, plus alignment. They are replaced in pairs across an axle either way, or the car brakes and corners unevenly. Electronically adaptive dampers cost far more, and a single unit can exceed a conventional pair.

Is it dangerous to drive with worn shock absorbers?

It is less immediate than a brake fault but it does lengthen stopping distances, because the tyres spend part of every bump lightly loaded or off the road entirely. It also undermines the ABS and stability systems, which assume the wheels stay planted, so the car becomes unpredictable in an emergency swerve. In the meantime the uncontrolled movement chews through tyres.

Cars this happens to most

Of every model with at least 2,000 tests in the DVSA data, these record shock absorber defective on the largest share of their MOTs. Across all of them the typical rate is 1.3% of tests.

1. Chrysler Ypsilon10%

   469 times in 4,474 tests

2. Fiat 500C10%

   2,483 times in 23,908 tests

3. Peugeot Bipper10%

   1,736 times in 17,324 tests

4. Citroen Nemo9.7%

   1,204 times in 12,371 tests

5. Fiat Qubo8.6%

   348 times in 4,033 tests

6. Vauxhall Adam8.0%

   4,682 times in 58,761 tests

7. Ford KA7.2%

   12,198 times in 169,345 tests

8. Abarth 5006.6%

   347 times in 5,235 tests

A high rate here is a property of the fleet as much as the car: these models skew old, and almost everything fails more with age. It is a reason to check the item on a used example, not proof the model is badly built. Models with fewer than 2,000 tests are left out because a rate drawn from a few hundred cars moves too much to rank.

Pass rates for every make and model →

Other common defects

• Direction indicator not working
• Stop lamp not working
• Lamp of the wrong colour, position or intensity
• Brake pipe corroded
• See all defects →